87 pick up not running ?

i have a 1987 chevy 1/2 ton 4x4 with a 5/7 v8 and dual tanks. do i need the selector valve to in order for the motor to run... i bypassed it and removed the driver side fuel tank and just put connectors connecting the fuel lines. now that i took of the selector valve it wont run or even give the fuel pump power to pump the gas but before i took it off it would get power. now the only way it runs is if i hook a wire going from the battery to the fuel pump. can anyone give me ideas on what to check to see if it is broken or w/e.. and all the fuses are fine.